This application is for renewal of a Sexually Transmitted Diseases Research Center Program Project. The overall objective is to focus the talents of investigators from a variety of disciplines on the overall problem of sexually transmitted diseases (STD's), and in specifically on questions related to the immunology and pathogenesis of selected sexually transmissible pathogens. We are requesting funding for the renewal of four currently funded projects and five core facilities, and for two additional projects. The currently funded projects are "Host response to gonococcal peptidoglycan", "Growth cycle dependence of chlamydial surface structure", "The Biology of Human Papillomavirus Type 6" and "Immune response in genital chlamydial infections". The projects which we would like to add are one which has as its objective elucidation of the mechanism by which Hepatitis B virus suppresses interferon production in infected cells, and one which has as its objective the development of mathematical models and computer simulations to study transmission patterns and effectiveness of interventions in sexually transmitted diseases with the initial emphasis on Chlamydia trachomatis infections. The Cores which would support the activities of these projects are Administrative, Clinical, Biostatistical, Immunology, and Chlamydial Culture. The Research Center has a close working relationship with the Bell Flower Clinic. It is through this facility that most of the clinical aspects of the research are conducted, and also that students, housestaff, and fellows, receive training in the diagnosis and management of STDs. The individual investigators of the center function as a closely integrated team with formal bi-weekly research conferences as well as a variety of informal groupings and interactions which are dictated by changing research interests.